Point to docker images used in the CI
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/docker/bionic/Dockerfile b/tests/docker/bionic/Dockerfile
index 3132be9..3c28685 100644
--- a/tests/docker/bionic/Dockerfile
+++ b/tests/docker/bionic/Dockerfile
@@ -4,6 +4,10 @@
# -------
# Defines a Docker container suitable to build and run all tests (all.sh),
# except for those that use a proprietary toolchain.
+#
+# WARNING: this Dockerfile is no longer maintained! See
+# https://github.com/Mbed-TLS/mbedtls-test/blob/master/README.md#quick-start
+# for the set of Docker images we use on the CI.
# Copyright The Mbed TLS Contributors
# SPDX-License-Identifier: Apache-2.0